Expansible jaw screw driver



y 23, s. BLOOMFIELD EXPANSIBLE ll AW SCREW DRIVER Filed Feb. 23, 1944 INVEN TOR.

Patented July 23, 1946 UNITED, STATES PATENT OFFICE Samuel Bloomfield, Wichita, Kans. Application February 23, 1944, Serial No. 523,519

This invention relates to hand tools of the type employed in moving to and from position, conventionalkerfed screws, bolts, machine screws and the like, the primary object being the provision of such an instrumenthaving as a part thereof, simple, rugged, inexpensive, unique and efiicient means for gripping the longitudinal side walls of the kerf gagement.

One of the important aims of the present invention is the provision of a hand tool of the aforementioned character that is in the nature of a screw driver having as a part thereof, resilient jaws, movable to engagement with the edges of a screw kerf as torque is applied to the screw driver shank in either direction about its longitudinal axis.

Another object of this invention is. to provide an inexpensive hand tool for manipulating screws, that embodies an assembly of interrelated parts at the blade end of the tool, which assembly is shifted to and from a normal position through the interaction of the manual manipulation of the tool and the means for yieldably engaging the said parts.

Other objects of theinvention include the specific manner of constructing the screw driver shank, the jaws associated therewith, and the means for yieldably holding the jaws in a normal position, all of which will appear during the course of the following specification, referring to the accompanying drawing wherein:

Fig. .1. is a condensed side elevational view of an expansible jaw screw driver, made to embody the features of the present invention.

Fig. 2 is a fragmentary side elevational view of a portion of the tool showing the jaws thereof in an expanded condition.

Fig. 3 is a fragmentary vertical sectional View through that portion of the tool shown in Fig; 2 but taken on line III--III of Fig. 1.

Fig. 4 is an enlarged stretch-out perspective view of the component parts of the screw driver.

Fig. 5 is an enlarged cross sectional view taken on line V-V of Fig. 1; and

Fig. 6 is a similar cross sectional view taken on line VIVI of Fig. 2.

One of the greatest problems experienced by users of screw drivers or similar tools that are employed in manipulating kerfed structural hardware, is the tendency of .the screw driver blade to slip from the kerf as force is exerted v about the longitudinal axis of the shank of the tool. This problem has'been prevalent for a considerto preclude accidental disen-' 3 Claims. (Cl. 145-50) v 2 able period of time and much effort has been expended in solving this aim.

The e'xpansible jaw screw driver illustrated herewith and about to be described, has been found to be eflicient, inexpensive to construct, andeasy to manipulate. a

The conventional screw driver about which parts. of'the tool embodying the invention may be assembled, comprises the well-known handle ill, from which extends a shank l2. In this instance, the shank is attenuated, cylindrical member, uniform in diameter throughout its length and with planar inclined, diametrically opposite faces l4 forming the blade portion of the tool. An annular groove l6 formed in shank I2 is spaced inwardly from faces M, as illustrated in Figs.'3 and 4.

The plurality of jaws that are loosely fitted upon shank I2, is, in this instance, a pair of semi-cylindrical jaws l 8 each having an internal contour conforming to that of the blade portion of shank I2 against which they are assembled. A head ZQis formed within each jaw [8 to enter groove [6.

When beads 20 of the two jaws H? are in the aforementioned relation with respect to fOove IS; the end of the blade formed by the convergence of'faces l4, rests immediately. above internal shoulders 22 formed on the jaws. When jaws l8 are so, positioned with respect to each other and the blade of shank 2, the specially formed split collar 24 is positioned as illustrated in Fig. 1." This split collar is aresilient annulus having at least two slits 26 provided therein that extend inwardly from that edge of collar 24 adjacent to the free end of shank l2.

The slits are designed as illustrated in Fig. 4 and when in the normal position, these slits progressively increase in width as their inner end is approached. Theseslits terminate in an enlargement 28, all to the end that" the split collar 24 may yieldably yet effectively hold the jaws l8 in a normal position but allow the expansion of the jaws, as hereinafter set down.

The outer edge of. jaws I8 formed by the meet-.

at 3!] to facilitate the placement of split collar 24 when the latter is moved downwardly over jaws l8. The frictional engagement between split collar 24 and jaws l8'will maintain these elements in a desirable working relation and against relative displacement. Well-known means may be utilized to secure collar 24 against longitudinal movement, if desired.

' gaging edge.

'3 Each jaw I8 is specially formed at itskerf en- A relatively short planarand knurled area 32 is ground, cast or otherwise formed to insure a positive grip between the opposed faces 34 of the kerf of screw 36. These areas 32 are in parallelism with faces 34 of the screw kerf and when the tool is manipulated in a normal fashion, these knurled areas 32 will be forcedagainst faces 34. e 7

The operation of the hand tool is obvious from the foregoing specification but it should be stressed that, advantage arise from the interengagement between internal shoulders 22 and the end of shank I2 formed by the meeting of faces l4. When a torque is applied to. causenthe, shank to move about its longitudinal axis, surfaces l4will act in a manner graphicallyv illustrated in Fig. 6, i. e; jaws l8 will be forced from claimed as new and desired to be secured b Letthe jaws; and resilient means engaging the jaws adapted to allow radial movement of the jaws as torque is applied to the blade, said jaws each having a shoulder engageable by the end of the blade as longitudinal force in one direction is applied to rthe'shank during use of the screw driver.

2. A screw driver of the character described 7 comprising, in combination, a handled shank having a blade at one end thereof and an annular groove formed therein adjacent to the blade;

the normal position shown in Fi 5 to the condition shown in Fig. 6, where knurled areas 32 are snugly and firmly pressed against the faces 340i 7 the kerf, Increasing the force of th torque will amplify the" outward pressure exerted between jaws I8 and they will be more'rigidly directedv against the opposed surfaces 34 to positivelypreclude accidental displacement. The application of such torque is sufficient to overcome the tension :of split collar 24 'andiwhen the tool is in operation the condition of jaws l8 and split colla'r 24.is asillustrated in, Fig. 2.. Release of the torque applying forcerwill permit collar to return jaws l8 to the normal position and the tool may be removed'from engagement with the screw kerfthe same asthollgh the gripping jaws were not present.- r i f-The use of theunique expandible jaws does not" add to the bulk of the tool to such an extent as to render its, use objectionable, and since the overall thickness of the screw engaging ends of "jaws 18 need not be greater than that of conventional screw drivers, the tool is usable :wherever a-standard screw driver could be employed.

' Any tendency'of the operator to exert downward pressure on shank l2 will not establish a;

'maladjustmentzbetween the parts. The end of shank; [2 will always rest upon shoulders 22 whether, the jaws are in. the normal position or spread in work.

The preferred embodiment of the invention has been illustrated and such modifications and alteration in specific structure as "are within the spirit of the invention may be made without departingfrom the scope of the appended claims.

Having-thus described the invention, what is a plurality of jaws loosely fitted; onto the blade and extending longitudinally therealong over the said groove; an internal bead on each jawrespectively, fittedTinto the groove to'preventlongitudinal displacement of the jaws; and resilientmeans engaging the jaw adapted toallow radialmovement ofthe'jaws as torque is applied to theblade, each of said .3 aws having a'shoulder formed.

on the inner; face thereof engageable by the end of the'blade when longitudinalfforce in one direcsnugly fit a length ofthe shank on each side of. the groove; a bead on each jaw fitted int the shank.

tion is exerted thereof, 1 I

3. A screw driver of the character described comprising, in combination, a handle,d,- 'attenuated, cylindrical shank having a pair of planar diametrically opposed, inclined faces 'forme'd thereon at one end'thereof; an annular groove formed in the shank spaced inwardly from the said inclined faces; a pair of opposed jaws each having. a cavity formed-thereincontoured to groove; a shoulder on each jaw to engage the end of the shank at the said inclined faces; and resilient means circumscribing the jaws to hold the same in place on the shank, the side edges of the planar faces on the shank serving to spread the jaws as torque is applied thereto during operation of the screw driver, the end of said shank and theshoulders on the innerfaces of the jaws being in engagement to cooperate with the inter-fitted groove and beads to prevent relative longitudinal movement of theshank and the jaws when longitudinal force in one direction 'is exerted on the eM L BLO ime:

on the screw driver during-use.- 

